Chemical processes



Patented June 25, 1946 CHEMICAL PROCESSES Wilbur A. Louie: and Frank K.Signaigo, Wilmington, DeL, assignors to E. I. du Pont de Nemours &Company, Wilmington, Del., a corporation of Delaware No Drawing.Application September 24, 1942, Serial No. 459,538

13 Claims. 1

This invention relates to a chemical process and more particularly itrelates to a catalytic process for the production of sulfur compounds.

Organic sulfur compounds, especially thiols, have become of considerableindustrial importance and methods for obtaining them economically andfrom readily available raw materials are of considerable utility. Estersof thioacids are a class of readily available sulfur derivatives that incertain cases can be hydrolyzed to produce thiols and other products.More often, however, the hydrolysis of esters of thioacids is notgenerally useful as a method for preparing thiols.

This invention, accordingly, has as an object to provide an economicalprocess for obtaining thiols. Another object is the preparation of thioland other valuable sulfur compounds from esters of thioacids. Otherobjects will be apparent from the following description of theinvention.

These objects are accomplished by reacting an ester of a thioacid withhydrogen over a sulfactive hydrogenation catalyst.

In practicing this invention an ester of a thicacid is charged into anautoclave, optionally with a suitable solvent, together with asulfactive hy-' drogenation catalyst, as for example, a sulfide of aferrous group metal. The contents of the autoclave are then agitated andheated under hydrogen at superatmospherlc pressure to a temperature ,atwhich hydrogenation takes place.

The optimum temperature for reaction varies with the particularthioester involved a hereinafter described, but usually a temperature offrom 100 to 300 C. is suitable. After the desired degree of'hydrogenation is obtained, the autoclave is cooled, the contentsfiltered to separate the catalyst, and the products are isolated by theusual methods of crystallization, distillation, solvent extraction, etc.

The following examples show in greater detail the practice of thiinvention. The amounts of materials referred to are expressed as partsby weight, unless otherwise specified.

Example I seventy parts of dodecyl thiosuli'ate (prepared by reacting adodecyl halide with sodium thicsulfate) is charged into an autoclave.together with 100 parts of ethanol and 7 parts of a suitactive cobalttrisulflde catalyst. Hydrogen is charged into the autoclave to apressure of 1500 lbs/sq. in., the autoclave is sealed, agitated andheated at 150 0. Rapid reaction ensues, as evidenced by the decrease inpressure and more hydrogen is added from time to time to maintain thepressure within the range of from 2000 to 2500 lbs/sq. in. After twohours of heating, no further hydrogen absorption is noted and theheating is continued for an additional hour to insure completion of thereaction. The autoclave is then cooled and the contents are filtered toseparate the catalyst. The clear solution is then diluted with water andextracted with ether. After removal of the ether from the ether extractby distillation, the oily residue is distilled. Thirty-two parts of puredodecanethiol-l boiling at 124 C. at 5 mm. are thus isolated. The yieldis 82% of theoretical. This reaction may be represented by the followingequation:

catalyst RSBOiNa Hg RSH NaOH ms IHIO The cobalt trisulflde catalyst usedabove is prepared as follows:

A solution or 240 parts of sodium sulfide nonahydrate and 64 parts ofsulfur in 1500 arts of Example II Fifty parts of dodecyl thiocyanate ischarged into an autoclave together with parts of henzone and 5 parts ofa sulfactive cobalt trisulflde catalyst, prepared as described underExample I. The autoclave is then charged with hydrogen atsuperatmospheric pressure and agitated and heated at C. After two hoursno further decrease in pressure is noted and the autoclave is cooled,the contents filtered from the catalyst, and fractionally distilled.There is thus obtained 25 parts of pure dodecanethiol-l corresponding toa yield of 80% The above experiment is repeated, except that 20 parts ofsulfur are charged into the autoclave together with the other reactantsand the hydrogenation is carried out at C. for four hours. In additionto dodecanethiol-l there are obtained methanethiol and ammonia as'by-products, instead of hydrocyanic acid as in the previous exp riment.These reactions may be formulated as follows:

Eighty-eight parts 01' n-butyi thiocaprylate is arged into an autoclavetogether with 75 parts benzene and 8 parts of a suli'active molybuumsulfide catalyst prepared by heating amnium thiomolybdate. The autoclaveis presred with hydrogen to 1000 lbs/sq. in. pressure, .tated and heatedto 1'15 C. During four hours a temperature is gradually increased to 250C. er which time the autoclave is cooled, the conits filtered from thecatalyst and iractionally tilled. After recovery 01' the benzene solventare is obtained a substantial proportion of huiethioi-l and minorproportions of. octyi thioirylate and unconverted butyl thiocaprylate.

Example IV )ne hundred parts of potassium n-butyl xanite, 100 parts ofwater and 10 parts 01' a suliaca cobalt sulfide catalyst, prepared asdescribed 39 Example I, are charged into an autoclave which :henpressured with hydrogen and heated at 0. As the reaction proceedsadditional hygen is added from time to time to maintain pressure withinthe range of from 1000 to 0 libs/sq. in. After two hours the autoclave:ooled and the gases bled through a receiver led with dry ice.Methanethiol condenses in receiver. The liquid contents of the autoclavefiltered from the solid material present. The d material is found toconsist of the cobalt ide catalyst mixed with polymeric thioiormallyde.The latter can be extracted from the alyst with boiling dioxane. Inaddition to the ducts already mentioned. butanol and higherlng thiolsare also formed. A possible course of se reactions may be represented bythe followequations:

enation autoclave together with 100 parts oi sane and parts of asulfactive cobalt sulfide dyst, prepared as described in Example I. Hy-

{en is charged into the autoclave at 1500 'sq. in. pressure, theautoclave sealed, and :ed at 150 C. for 4 hours, after which time no herhydrogen absorption is noted. The cons of the autoclave are filteredfrom the cataand the dioxane is distilled from the reaction ture. Theless volatile material consists or 35 s of oil, which is identified asdodecanethiol xidation to the solid crystalline disulfide meltat 35 to36 C. This reaction may be formu- :l as follows: I

4 clave is cooled and the products are filtered from the catalyst. Afterremoval of the dioxane, the primary product 01' reaction,beta-aminoethanethiol, a white solid, is sublimed from the reactionmixture under reduced pressure. In addition to this aminothiol there isalso obtained a fraction boiling at 40 C. at 5 mm. consisting mainly ofthiazoline. The formation oi these products presumably occurs accordingto the following equations:

soc-N HgC-N Bic-N csH an, mNomcmsH Ginsu Inc-s Example VII One hundredparts of 2-mercaptobenzothiazoie, and parts of dioxane are hydrogenatedin an autoclave with 10 parts of a sulfactive cobalt sulfide catalyst,prepared as described in Example I, at C. and 1400 to 2200 lb./sq. in.pressure for 5 hours. Considerable hydrogen is absorbed and the pressureis maintained within the specified range by the addition of hydrogen asneeded. Distillation of the reaction product yields a yellow oil boilingat 87 to 100. C. at .8 mm. pressure. This oil is found to consist of amixture in nearly equal proportions of o-aminothiophenol andbenzothiazole. The aminothiol is separated from the thiazole byextraction with aiqeuous alkali and regenerated from the alkalinesolution by neutralization with acid. The alkali insoluble thiazolefraction may contain some benzothiazoline. In addition to these productssome unconverted mercaptobenzothiazole is recovered.

By operating at 0. complete conversion of the mercaptobenzothiazole isaccomplished. In addition to the aminothiol and thiazole there is alsoformed at the higher temperature, some aniline.

Although the foregoing examples have illustrated specific embodiments ofthis invention, the invention is also applicable to the hydrogenation ofother esters of thioacids. In general, these may be represented by theformulae:

wherein R stands either for an aliphatic, alicyclic or aromatic radicaland which may contain, in

,carboxyl, nitro, mercapto, etc., X represents a monoor polybasicthioacid radical, and Y represents a polybasic thioacid radical.Specific types of esters of thioacids coming within the scope of theabove formulae are the following:

A. Esters of thiosulfuric acid (RSSOaNa. RaSzOa)- Examples 0! esters ofthis type are octyl thiosuli'ate. dioctyl thiosulfate, dodecylthiosuli'ate, octadeoenyl thiosuliate, hexamethylenebisthiosuliate,benzylthiosuliate, N-phthalimidoethyl thiosulfate. The principal productof the hydrogenation of the estersoi' this type is the correspondingthiol.

B. Esters oi thiocyanic acid (RSCN). Specific thiocyanates are butylthiocyanate, aliyl thiocyanate, decamethylene-bisthiocyanate, octadecylthiocyanate, phenyl thiocyanate', benzyl thiocyanate, p-nitrohensylthiocyanate and naphthyl thiocyanates. The hydrogenation of thiocyanatesyields the corresponding thiols together with hydrocyanic acid ormethanethiol.

C. Esters of carbothioic acids (RCOSR', RSCOR', RCSSR'). Examples ofesters of this type which may be hydrogenated according to the processof this invention are tate, allyl thiobutyrate, amyl thiocapyrlate.Phenyl thioacetate, benzyl hydroxy-thioacetate, ethyl dithioacetate, andbutyi thionovalerate. Hydrogenation oi carbothioates, according to thisinvention, yields thiols, esters, aldehydes, and sulfi es.

D. Monothiocarbonates (RSCOOM, ROCOSM, RSCOOR', where M=a metal ion).Specific examples of esters of this type are s-cyclohexyl ethylmonothiocarbonate, diethyl monothiocarbonate, sodium phenylmonothiocarbonate, etc.

E. Esters oi' dithiocarbonic acid (RSCOSM, ROCSSM, RSCOSR'). Included inthis group of esters are the xanthates such as potassium ethyl xanthate.potassium dodecyl xanthate, sodium octyl xanthate, sodium cellulosexanthate (viscose) ethyl sorbityl dithiocarbonate, and the like. Thehydrogenation of the esters of dithiocarbonic acid according to theprocess of this invention yields thiols, alcohols, and mercaptomethylcompounds.

F. Esters of trithiocarbonic acid (RSCSSM and RSCSSR). Examples oftrithiocarbonates are dibutyl trithiocarbonate, didodecyitrithiocarbonate, ethylene trithiocarbonate and the like. Hydrogenationof trithiocarbonates according to the process of this invention yieldsthiols.

G. Esters of monothiocarbamic acid (BBCONBI, BOCSNH: and RBOONH)monothiocarbamic esters are: B-octyl S dodecylthiocarbamate, etc.monothiocarbamates yields Specific thiocarbamate, The hydrogenation of'thiols, mercaptomethyl compounds, etc,

Specific examples of dithiocarbamates are S-octyi dithiocarbamate,N-hexamethylene-bis-cthyldithiocarbamate, and the cyclic N-substitutedesters of dithiocarbamic acid, which are known better as mercaptothiazoies or mercapto thiaaolines, as for example, 2-mercaptothiazoline,mercaptobenzothiazole. The products of the hydrogenation of thedithiocarbamates include thiols, and, in the case of the cyclicmercaptothianolines and thiazoles, heterocyclic compounds andaminothlols.

Although not essential in many cases solvents may be employed incarrying out the hydrogenation process. Examples of solvents that may beused are water, and organicv solvents such as hydrocarbons, alcohols,ethers, and the like. Instead of or in addition to inert solvents,alkalis, ammonia, amines and acids may be present if desired.

The process of this invention may be operated over a considerable rangeof temperatures. Generally speaking, a suitable reaction temperaturewill be found within the range from 100' to 300 C. In the higher temprature range the reaction proceeds more rapidly so usually it ispreierred to employ temperatures of at least 125' C. when the desiredproduct or the reaction is that corresponding to complete hydrogenationof the ester of a thioacid employed as starting mate- 4.. .im .1...-mnmmtures oi the order of 175 vinyl thiolacegust 23, 1940.

-to 250 C, are preferred. When it is desired to obtain intermediatereduction products. as ior example, mercaptomethyl compounds'from thethiocarbonates and thiazoles and thiazollnes from the carbamates, it ispreferred to hydrogenate at the minimum temperature required forreaction at a practical rate, usually in the neighborhood of to C. Forthe hydrogenation of esters of thiocarboxylic acids, that is thecarbothioates, higher temperatures are required usually above 200' C.

In most cases the reaction proceeds well even at low pressures ofhydrogen, but in order to insure a practicable rate of reaction, it isdesirable to operate at a hydrogen pressure of at least 100 lbs/sq. in.Purified hydrogen is not essential for the practice of this invention,and instead, hydrogen mixed with other gases, such as nitrogen, hydrogensulfide, etc., may be used.

By the term "sulfactive hydrogenation catalyst" as used herein and inthe claims, we mean a catalyst prepared as described in U. S. PatentsNos. 2,221,804 and 2,230,390, and which is active for the catalytichydrogenation of the sulfur in organic multisulfides, organic sulfurcompounds having carbon to sulfur unsaturation, and organic sulfurcompounds having sulfur to ozwgen unsaturation.

Examples of sulfactive catalysts that may be used in carrying out theprocess of this invention are sulfides oi the base metals such aschromium. cobalt, copper, iron, lead, molybdenum, nickel, tin, tungsten,and vanadium. It is preferred, however, to use sulfides of the metalscobalt, molybdenum, nickel, and iron, since these have been found to beexceptionally active. Such catalysts may be prepared as described in thecopending applications of F. K. Signaigo, Serial Nos. 319,241 and319,242, filed February 16, 1940, and that of B. W. Howk, Serial No.353,936, filed Au- For example, the metal sulfide may be precipitatedfrom a solution of a metal salt with hydrogen sulfide, a solution ofalkali or alkaline earth metal sulfides or polysulfides or with ammoniumsulfide or polysulfides. Another method that has been found to yieldvery active hydrogenation catalysts is to treat the finely dividedpyrophoric or activated metal with hydrogen sulfide or sulfur untilsulfidatlon is substantially complete. Other methods for obtaining metalsulfide catalysts include heating powdered metals or metal compoundssuch as the oxides. carbonates or sulfides with volatile sulfidingagents such as sulfur, hydrogen sulfide, or carbon bisulfide.

The hydrogenating activity of metal sulfides may be increased in manyinstances by treatment with hydrogen at elevated temperature. Thehydrogen treatment of the metal sulfide often can be combinedconveniently into a single operation with the hydrogenation reaction forwhich the catalyst is to be used. Instead of charging the metal sulfideas such it may be formed in situ by placing the finely dividedpyrophoric or activated metal in the autoclave together with sulfur orhydrogen sulfide. The metal will then be converted to the active metalsulfide during the early stages of the reaction process. The catalystemployed may be substantially a pure metal sulfide or a combination ofmetal sulfides. Other substances may be present also as, for example,kieselguhr, alumina. magnesia, carbon. and other supporting or promotormaterials.

Usually an amount of sulfactive catalyst of II from i to 15% by weightof the ester to be con- 7 verted will produce a satisfactory rate 01reaction, although other proportions may be employed as convenient.

The process oi this invention may be operated batchwise or in acontinuous manner. In the latter case, the catalyst is preferably formedinto rigid lumps and the ester, either in the liquid or vapor phase, ispassed over the catalyst together with the hydrogen.

By the process of this invention esters of thioacids are economicallyconverted into the more reactive thiols and other valuable sulfurcompounds. which find use as intermediates in the manufacture ofinsecticides, rubber chemicals, dyestufis. petroleum addition aaents,and the like.

As many apparently widely diiierent embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that this invention is not to be limited to the specificembodiments shown and described.

Wh claim:

L The process for the Production of thiols. which comprises reacting anester of a thioacid with hydrogen in the presence of a suliactivehydrogenation catalyst.

2. The process ior the production 01' thiols, which comprises reactingan ester oi a thiocyanic acid with hydrogen in the presence of asuliactive hydrogenation catalyst.

3. The process for the production or thiols. which comprises reacting anester 01' a thiocarbamic acid with hydrogen in the presence of asuli'active hydrogenation catalyst.

4. The process for the production of thiols.

Pets 'No. 2,402,642.

WILBUR AQLAZIER ET AL.

8 which comprises reacting an ester of a dithiocarbamic acid withhydrogen in the presence 01' a sulfactive hydrogenation catalyst.

is. The process in accordance with claim 4 characterized in that theester is a cyclic ester of dithiocarbamic acid.

8. The process for the'production of betaaminoethanethiol. whichcomprises reacting 2- mercapto-thiasoline with hydrogen in the presonceof a suli'active hydrosenation catalyst.

'l. The process which comprises reacting an ester oi a thiocarbic acidwith hydrogen in the presence oi a suliactive hydrogenation catalyst.

8. The process in accordance with claim 1 characterized in that thesuli'active hydrogenation catalyst is a metal sulfide.

9. The process in accordance with claim 1 characterized in that thesulfactive hydrogenation catalyst is a sulfide or a metal of the irongroup 0! the periodic table.

10. The process in accordance with claim 1 characterized in that thesuli'active hydrogenation catalyst is a cobalt sulfide.

11. The process in accordance with claim 1 characterized in that thesuliactive hydrogenation catalyst is a molybdenum sulfide.

12. The process for hydrogenating an ester of a thio acid whichcomprises reacting said ester with hydrogen in the presence of aslllfactive hydrogenation catalyst.

13. The process in accordance with claim 12 characterized in that thereaction is carried out at a temperature in the range of 100 to 300 C.

WILBUR LAZIER.

A. FRANK K. BIGNAIGO.

Certificate of Correction June 25, 1946.

It is herebycertified that error appears in the printed specification ofthe above numbered patent requiring correction as follows: Column 8,

that the said Letters Patent "thiocarbic read thz'ocarbom'c; and

line 12, claim 7, for should be read with thiscorrection therein thatthe same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 8th day of October, A. D. 1946.

LESLIE FRAZER,

First Assistant Commissioner of Patents.

7 verted will produce a satisfactory rate 01 reaction, although otherproportions may be employed as convenient.

The process oi this invention may be operated batchwise or in acontinuous manner. In the latter case, the catalyst is preferably formedinto rigid lumps and the ester, either in the liquid or vapor phase, ispassed over the catalyst together with the hydrogen.

By the process of this invention esters of thioacids are economicallyconverted into the more reactive thiols and other valuable sulfurcompounds. which find use as intermediates in the manufacture ofinsecticides, rubber chemicals, dyestufis. petroleum addition aaents,and the like.

As many apparently widely diiierent embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that this invention is not to be limited to the specificembodiments shown and described.

Wh claim:

L The process for the Production of thiols. which comprises reacting anester of a thioacid with hydrogen in the presence of a suliactivehydrogenation catalyst.

2. The process ior the production 01' thiols, which comprises reactingan ester oi a thiocyanic acid with hydrogen in the presence of asuliactive hydrogenation catalyst.

3. The process for the production or thiols. which comprises reacting anester 01' a thiocarbamic acid with hydrogen in the presence of asuli'active hydrogenation catalyst.

4. The process for the production of thiols.

Pets 'No. 2,402,642.

WILBUR AQLAZIER ET AL.

8 which comprises reacting an ester of a dithiocarbamic acid withhydrogen in the presence 01' a sulfactive hydrogenation catalyst.

is. The process in accordance with claim 4 characterized in that theester is a cyclic ester of dithiocarbamic acid.

8. The process for the'production of betaaminoethanethiol. whichcomprises reacting 2- mercapto-thiasoline with hydrogen in the presonceof a suli'active hydrosenation catalyst.

'l. The process which comprises reacting an ester oi a thiocarbic acidwith hydrogen in the presence oi a suliactive hydrogenation catalyst.

8. The process in accordance with claim 1 characterized in that thesuli'active hydrogenation catalyst is a metal sulfide.

9. The process in accordance with claim 1 characterized in that thesulfactive hydrogenation catalyst is a sulfide or a metal of the irongroup 0! the periodic table.

10. The process in accordance with claim 1 characterized in that thesuli'active hydrogenation catalyst is a cobalt sulfide.

11. The process in accordance with claim 1 characterized in that thesuliactive hydrogenation catalyst is a molybdenum sulfide.

12. The process for hydrogenating an ester of a thio acid whichcomprises reacting said ester with hydrogen in the presence of aslllfactive hydrogenation catalyst.

13. The process in accordance with claim 12 characterized in that thereaction is carried out at a temperature in the range of 100 to 300 C.

WILBUR A. LAZIER. FRANK K. BIGNAIGO.

Certificate of Correction June 25, 1946.

It is herebycertified that error appears in the printed specification ofthe above numbered patent requiring correction as follows: Column 8,

that the said Letters Patent "thiocarbic read thz'ocarbom'c; and

line 12, claim 7, for should be read with thiscorrection therein thatthe same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 8th day of October, A. D. 1946.

LESLIE FRAZER,

First Assistant Commissioner of Patents.

